posted on 2024-04-02, 19:43authored byWenzhe Yu, Li Luo, Xiangyu Qi, Yuman Cao, Jie An, Zhiguo Xie, Tianming Hu, Peizhi Yang
Plant growth-promoting rhizobacteria have been shown
to enhance
plant tolerance to drought stress through various mechanisms. However,
there is limited research on improving drought resistance in alfalfa
by genetically modifying PGPR to produce increased levels of cytokinins.
Herein, we employed synthetic biology approaches to engineer two novel
strains of Sinorhizobium meliloti capable
of overproducing trans-Zeatin and investigated their potential in
enhancing drought tolerance in alfalfa. Our results demonstrate that
alfalfa plants inoculated with these engineered S.
meliloti strains exhibited reduced wilting and yellowing
while maintaining higher relative water content under drought conditions.
The engineered S. meliloti-induced
tZ activated the activity of antioxidant enzymes and the accumulation
of osmolytes. Additionally, the increased endogenous tZ content in
plants alleviated the impact of drought stress on the alfalfa photosynthetic
rate. However, under nondrought conditions, inoculation with the engineered S. meliloti strains had no significant effect on
alfalfa biomass and nodule formation.